The polar vortex is descending on the midsection of the United States, bringing bitterly cold Arctic air and causing temperatures to plunge rapidly in many areas. The deep freeze will be accompanied by a major snowstorm that is expected to cause travel chaos. The vortex is a large rotating expanse of cold air that generally circles the Arctic, but occasionally shifts south from the pole. …So when the vortex meanders southward, two basic questions arise. What role, if any, does climate change play? And will extreme freezes increase as warming continues? The short answer: Scientists aren’t sure, yet.

What is the polar vortex, exactly? Some scientists have compared it to a spinning top. The vortex is encircled by the polar jet stream, a band of winds that blows from west to east around the planet. …But just as a spinning top can start to wobble and drift if it bumps into something, the vortex can be disrupted. …If the movement is rapid enough, temperatures in the areas exposed to the mass of cold air can fall by tens of degrees within hours, and can stay extremely low for days or even weeks until the vortex becomes stable again in the North Pole region.